1. Technical Field
Aspects of the present invention relate to mass spectrometers, to mobility spectrometers, and to ion sources that can operate approximately at ambient pressure, and more specifically, to a “curtain-gas filter”.
2. Related Art
Related art investigations of large molecules may employ mass spectrometers and mobility spectrometers. Related art mass spectrometers investigate the deflection of molecule ions in electromagnetic fields and so determine the molecule weight, which is approximately proportional to the volume of the molecule under investigation. Related art mobility spectrometers investigate the speed of an ion when dragged through a buffer gas, a quantity which is approximately proportional to the cross section of the molecule under investigation.
For the related art systems, selection of the ion source is important. Commonly used ion sources for large molecules include “electrospray ion sources (ESI)” as disclosed in J. B. Fenn, JASM 4 (1993) 524 and sources for “matrix assisted laser desorbed ion sources (MALDI)” as disclosed in M. Karas, F. Hillenkamp, Anal. Chemistry 60 (1988) 2299 as well as sources for “electrospray-assisted laser desorbed ion sources (ELDI)” as disclosed in M. Z. Huang, H. J. Hsu, J. Y. Lee, J. Jeng, J. Shiea, J. Prot. Res. 5 (2006) 1107, or “desorption electrospray-ion sources (DESI)” as disclosed in Z. Takats, J. M. Wiseman, B. Gologan, G. Cooks Science 306 (2004) 471. These sources may be used at elevated pressures, including at atmospheric pressure. However, other related art ionization methods in other “atmospheric pressure ion sources (API)” can be used as well.
Related art investigations of molecules have become important in applications related to biology, medicine and pharmacology. These related art techniques allow characterization of a molecule not only by weight and cross section but also by structure, which becomes apparent by investigating the fragments into which a molecule will break when it absorbs energy, for example, by collisions with buffer gas molecules or atoms.
A curtain gas filter that operates with low flux ion sources is disclosed in U.S. patent application No. 61/103,168 and International Application no. PCT/US2009/057281, which are each incorporated herein in their entirety by reference.